My homebuilt spindles

[tskguy]

What ever happened with this? I am in the middle of the gathering parts for a spindle and I am interested in how this one played out?

Eric

[RotarySMP]

Hi Eric,

What happened? Summer came along and I have been doing other things Machining is a pretty seasonal hobby. Spring and Autumn are productive, summer there are too many other nice things to do, and winter is too cold on the balcony.

Current status is that I need to order some pulleys and a belt, machine up the motor mount, and come up with the power supply that works.

My plan to use a hacked ATX computer PSU isn't working as the motors have too little coil resistance, and the PSU sees a short and trips off line.

[tskguy]

Completely understand!!

I just ordered a ER16 12mm shaft collet and have bid on a pair of Super precision AC bearings! I'm just having some trouble working out the housing...Should I do stainless or free machining steal or aluminum or a combo!! I'm not that good at cutting threads so I'm not sure what to do in terms of a end cap like you have done. Decisions decisions....
I know for sure I plan on using a brushless inrunner and a heli speed control.
I also plan on doing some sort of belt driven thing to change rpm torque curves.
Anyway some of your threads have been very helpful!

Eric

[RotarySMP]

Hi Eric,

An ER16 collet but only a 12mm shaft? You will have to be careful to limit the overhang between the spindle nose and the bearings. My next spindle will be ER-16 but I bought a 20mm shaft version.

The loads on the housing are minimal, but thermal expansion has to be considered. That speaks against Aluminium housing/steel shaft.

I would go for free machining steel (if I wasn't so cheap). The steel I used was use was in the cheap offcut bin of my steel dealer. If you consider the stress of mucking around trying to get good threads (with crap equipment) in tough steel, I would have been miles ahead if I had just paid a few extra bucks for leaded free machining steel.

All steels have roughly the same Youngs modulus, so the rigidity is the same regardless which flavour you use.

I went for a screw on cap becuase I have the lathe at home, but my mill and rotary table are an hours drive away. If you have a mill and rotary table, you can do the end caps with bolted flanges.

What equipment do you rhave available?

Did you see http://www.metallmodellbau.de/Eigenb...salspindel.php

[tskguy]

mmmm I hope the 12mm shaft will be ok! I went with it because I found those bearings cheap. Thanks for that link it looks very close to what I was thinking.
As for equipment I have my desktop mill/router and A 7x10 mini lathe.
The lathe is capable of cutting threads I'm just not!!! I guess I could try

I am fairly new to machining so cutting threads is a little scary.

I really never thought about thermal expansion I guess going with the machining steel will be the best option.

[RotarySMP]

Well, summers over, so I have started machine things again.

First off, I finally turned a thread (35x1mm) in the end of my ER-32 milling spindle, and then made up a pair of lock nuts for it.

[RotarySMP]

I took Herberts advice and sourced a better motor than those €3 Johnsons. This is an Astro Cobalt 25 I picked up off Ebay.

I have it running off a hacked 420W ATX Psu and a Chinese PWM speed controller. It seems pretty powerful - The spec sheet lists a peak of 480W at 19 000 rpm and 17V. I won't be running it that hard.

I turned up an eccentric ring with a 2mm throw for the motor out of Aluminium, and have started making the motor mount from 12mm mild steel.

I used the Maedler.de tooth belt selection tool to find three gear ratios which will work with the 2mm adjustment, and standard length belts. Ended up choosing the same MXL system as Achim:
Universalspindel die Zweite, oder es geht auch flüsterleise und kompakt

24:20 with a 162,56mm belt
24:30 with a 172,72mm belt
24:60 with a 203,20mm belt

I found a good speed and feed and got a really nice finish on the bores with TCMT090202 inserts. Next I need to take it out to the mill to finish the outer profile and slit the rings.

[RotarySMP]

Today I made the seals which go in the end caps.

These were turned from Ikea cutting pads. Cheap source of engineering plastic sheet.

Haven't got around to ordering the belts and pulleys from Maedler yet, as this is below their minimum order, so have have to finish the design on a couple other things which will also need parts from Maedler.